Method of operating a rotary kiln



July 8, 1941.

Patented July 8, 1941 UNITED STATES PATENT OFFICE 2,248,039 METHOD F OPERATING A ROTARY KILN Niles M. Anderson, Tacoma, Wash.

Application September 21, 1938, Serial No. 231,031

2 Claims.

This invention relates to an improvement in rotary kilns and the method of operating the same and has for its purpose to avoid trouble'- some rings caking upon the interior wall of the kiln.

While the difllculties encountered and the improved method of overcoming these difficulties applies to the burning of other materials in rotary kilns, for simplicity, it will be described in connection with the burning of lime.

In the usual practice in burning lime in rotary kilns, the material to be burned is introduced into the upper end of the kiln in the form of slurry and is rst dried and then burned as it moves towards the lower or exit end of the kiln. When the material becomes suiciently dried and before it is burned, there is a tendency for it to cake upon the wall of the kiln. Frequently, it accumulates at such a' place and forms a ring, which constitutes a partial dam for the following material and increases the caking thereof. The ring may continue to build up until some means has to be provided for its removal.

Various methods have been employe-d including the stopping of the kiln and flowing water therethrough to wash out a ring which is not too badly caked, the shooting of the ring with a shot gun or a machine gun to break it up, and the shutting down and cooling off of the kiln to allow a man to enter and chop out the ring where other methods fail.

As just indicated, the addition of moisture has a tendency to disintegrate the ring as it rst forms or in its incipient stages. Also, greater heat which will burn the carbonate to oxide at the incipient stages of ring formation tends to disintegrate the ring. I have discovered that by moving the burner longitudinally of the kiln, the` belt Where a ring might otherwise form may be kept clear by alternately moving the burner towards the exit end of the kiln and thereby subjecting the said belt to a greater degree of moisture and then moving the burner towards the entrance end of the kiln and thereby burning to the oxide any carbonate which has formed in the ring. In this way, the troublesome formation of rings in burning lime slurry in a rotary kiln can be substantially eliminated.

In the accompanying drawing forming a part of this specification, there is indicated at l a portion of a rotary kiln which may be of any suitable form', the kiln being provided with a refractory lining 2. At the exit end of the kiln there is the usual hood 3. Diagrammatically indicated there is a burner tip 4 adapted to burn oil or gas. The burner is shown mounted upon a pipe 5 which may receive fuel, air, steam, or the like through pipes 6 and 1. 'I'he pipe is slidably mounted in a suitable support 8 and may be clamped in position by a screw 9 or the like'. It will be readily understood that obvious modications can be made in the mounting of the burner and the pipe supporting it, the essential point being that the burner is mounted so as to be movable longitudinally of the axis of the kiln.

With a construction such as described, it will be readily seen that the position of the burner may be adjusted from time to time longitudinally of the kiln so as to prevent the formation of a ring, or to break up such a ring in its incipient stages. It will also be readily understood that while this process and apparatus has been described in connection with the burning of lime, that a similar method and apparatus may be employed for the prevention or breaking up of rings on rotary kilns where other materials are being burned and where a similar difliculty with ring formation is encountered. It will be understood, of course, that the products of combustion flow through thel kiln to the end where the material enters the kiln to be treated in the usual manner, and that any obvious or usual construction may be employed at the entrance end of the kiln to admit material to be burned and provide for the exit of products of combustion and steam or other vapors or gases produced during the burning operation, and at the exit end of the kiln to provide for the discharge of the burned material. Also, the kiln will be supported and rotated in any convenient way, these features being old and well known and, therefore, not requiring illustration.

What I claim is:

1. The method of operating a rotary kiln which comprises introducing into the charging end of the kiln material which tends to cake onto the wall of the kiln at one stage of its burning, directing flame towards the charging end from a source Within, and at the axis of, the kiln, and shifting the flame longitudinally of the axis of the kiln and thereby changing the location where the material reaches the caking stage.

2. T-he method of operating a rotary kiln which comprises introducing lime slurry into the charging end of the kiln, directing flame towards the charging end along and spreading symmetrically from the axis of the kiln, heating the lime during its passage through the kiln to and past a stage at which it tends to cake onto' the wall of the kiln, and shifting the flame longitudinally of the axis of the kiln and thereby varying the location where the lime reaches the caking stage.

NILES M. ANDERSON. 

